Method for Optimization of Joint Arthroplasty Component Design

ABSTRACT

Methods and devices are disclosed for the optimization of shoulder arthroplasty component design through the use of computed tomography scan data from arthritic shoulders.

CROSS-REFERENCES TO RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.15/429,037, filed Feb. 9, 2017, which is a continuation application ofU.S. patent application Ser. No. 15/063,021, filed Mar. 7, 2016, whichis a continuation application of U.S. patent application Ser. No.13/818,738, filed Feb. 25, 2013, now U.S. Pat. No. 9,278,413, which is a371 national stage entry of PCT International ApplicationPCT/US2011/49686 filed Aug. 30, 2011, which claims the benefit of U.S.Provisional Patent Application 61/379,222, filed Sep. 1, 2010 and U.S.Provisional Patent Application 61/379,634 filed Sep. 2, 2010, which areincorporated herein by reference for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a method for the optimization of jointarthroplasty component design, and more particularly to a method for theoptimization of shoulder arthroplasty component design through the useof computed tomography scan data from arthritic shoulders.

2. Description of the Related Art

Various prostheses for the replacement of the shoulder joint are known.In one example shoulder prosthesis, the upper portion of the humerus isreplaced by a humeral component including (i) a stem that extends into abore formed within the humerus and (ii) a generally hemispherical headportion that is connected to the stem. The hemispherical head of thehumeral component articulates with a complementary concave section of aglenoid component mounted within the glenoid cavity of the scapula. Thistype of shoulder prosthesis may be called a “primary” or “total”prosthesis. In another example shoulder prosthesis, often called a“reverse” or “inverted” prosthesis, the glenoid component includes aconvex section that articulates with a complementary concave section ofthe head of the humeral component.

One alternative to total shoulder replacement is referred to as shoulderhem iarthroplasty. In one version of this procedure, the humeral head isreplaced with a generally hemispherical head that may or may not includea connected stem. The glenoid cavity of the scapula is not replaced witha glenoid component, but may be refinished in a way that gives it asmooth surface and a shape which matches the generally hemisphericalreplacement head. Another version of this procedure can use a glenoidcomponent with resurfacing of the humeral head.

Several deficiencies have been found in currently available shoulderarthroplasty systems including glenoid sizes (primary and reverse) andhumeral sizes that are not based on the anatomic distribution. Inaddition, the advent of reverse arthroplasty for the treatment ofproximal humerus fractures has also changed the requirements for anappropriate fracture stem. Specific design features are necessary tomake the fracture stem appropriate for hem iarthroplasty and reversearthroplasty use. Although resurfacing of the humerus has becomepopular, the designs are not based on an anatomic distribution. Theinstrumentation that is currently available is inadequate and may leadto significant malposition in version and inclination.

Prior magnetic resonance imaging and cadaveric studies of glenohumeralanatomy have been performed on shoulders without arthritis (lannotti etal., “The normal glenohumeral relationships. An anatomical study of onehundred and forty shoulders”, J Bone Joint Surg Am. 1992; 74:491-500;Hertel et al., “Geometry of the proximal humerus and implications forprosthetic design”, J Shoulder Elbow Surg., July/August 2002, pp.331-338; and Boileau et al., “The Three-Dimensional Geometry Of TheProximal Humerus—Implications For Surgical Technique And ProstheticDesign”, J Bone Joint Surg [Br], 1997; 79-6:857-865). However, inreality, shoulder arthroplasty is not performed on normal shoulders.Shoulder arthroplasty is performed in patients with arthritis in thesetting of cartilage loss and usually associated bone loss. In order tomake properly sized implants that will accommodate patients witharthritis, it is important to understand the anatomy of these patients.

Typically, the designing surgeon has used a system with three glenoidsizes. In one study, it was determined that the distribution of glenoidcomponents used in total shoulder arthroplasty was as follows: 4% large,40% medium, and 56% small. One can see that based on component use, thesizing of these implants is not optimal. If glenoid component sizes arenot optimal, there may be issues related to perforation of the glenoidby fasteners used in attaching the glenoid component to the scapula. Inaddition, certain components may be too large for smaller patientsresulting in component overhang and potentially leading to violation ofimportant neurovascular structures. Thus, it could be hypothesized thatthe preference for small glenoid components may result from the desireto avoid glenoid perforation and/or avoid component overhang. However,larger glenoid components can lead to a better fitting prosthesis andgreater stability.

Thus, there exists a need for a method for the optimization of jointarthroplasty component design, and in particular, there exists a needfor a method for the optimization of shoulder arthroplasty componentdesign.

SUMMARY OF THE INVENTION

The present invention addresses the foregoing needs by providing methodsfor the optimization of joint arthroplasty component design.

In one aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. The method comprises: (a) obtaining an axial image of the boneof the joint; (b) orienting on the image a reference angle from a bodyof the bone to create a neutral face plate line that extends from afirst border of the bone to an opposite second border of the bone; (c)measuring a length of the neutral face plate line; and (d) manufacturingthe prosthetic component to include a base surface and an opposedarticular surface wherein a width of the base surface is a predeterminedpercentage of the length of the neutral face plate line. For example,the width of the base surface may be the same or less than the length ofthe neutral face plate line.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. The method comprises: (a) obtaining an axial image of the boneof the joint; (b) orienting on the image a reference angle from a bodyof the bone to create a neutral face plate line that extends from afirst border of the bone to an opposite second border of the bone; (c)orienting on the image a first reference line perpendicular to theneutral face plate line and extending over the bone in the image; (d)measuring a first reference length of the first reference line from theneutral face plate line perpendicular to a depth of a cavity in thebone; and (e) manufacturing the prosthetic component to include anarticular section and a projection extending away from the articularsection wherein a length of the projection is a predetermined percentageof the first reference length. For example, the length of the projectionis typically less than the first reference length.

In another aspect, the invention provides a method for manufacturing aglenoid component for replacing a part of a scapula of a shoulder jointin a subject, the method comprises: (a) obtaining a sagittal image ofthe glenoid of the scapula; (b) orienting on the image a first referenceline that extends perpendicularly from an inferior border of the glenoidimage over the scapula in the image; (c) orienting on the image a secondreference line that perpendicularly intersects the first reference lineand that extends from a first border of the scapula to an oppositesecond border of the scapula; (d) measuring a length of the secondreference line; and (e) manufacturing the glenoid component to have awidth that is a predetermined percentage of the length of the secondreference line. For example, the width of the glenoid component may bethe same or less than the length of the second reference line.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. The method comprises: (a) obtaining a coronal image of the boneof the joint; (b) orienting on the image a first reference line thatextends from a first border of a head of the bone to an opposite secondborder of the head of the bone; (c) orienting on the image a 90 degreereference angle from an inferior position of the first reference line tocreate a second reference line that extends over the image of the bone;(d) orienting on the image a third reference line that extends over theimage of the bone from the second reference line to a superior aspect ofa tuberosity of the bone; (e) measuring a length of the third referenceline; and (f) manufacturing the prosthetic component to include aprotruding section wherein a length of the protruding section is apredetermined percentage of the length of the reference line.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. The method comprises: (a) obtaining a coronal image of the boneof the joint; (b) orienting on the image a first reference line thatextends from a first border of a head of the bone to an opposite secondborder of the head of the bone; (c) orienting on the image a ninetydegree reference angle from an inferior position of the first referenceline to create a second reference line that extends over the image ofthe bone; (d) orienting on the image a third reference line that extendsover the image of the bone from the second reference line to a superiorborder of a tuberosity of the bone; (e) orienting on the image a fourthreference line that extends over the image of the bone from the thirdreference line to a side border of the tuberosity of the bone; (f)measuring a length of the fourth reference line; and (g) manufacturingthe prosthetic component to include a protruding section wherein adiameter of the protruding section is a predetermined percentage of thelength of the fourth reference line.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. In the method, the prosthetic component is formed to include abase surface and an opposed articular surface wherein a width of thebase surface is a predetermined percentage of a length of a neutral faceplate line. The length of the neutral face plate line used by themanufacturer in forming the prosthetic component has been determined by(i) obtaining an image of the bone of the joint, (ii) orienting on theimage a reference angle from a body of the bone to create the neutralface plate line, wherein the neutral face plate line extends from afirst border of the bone to an opposite second border of the bone, and(iii) measuring the length of the neutral face plate line. Thepredetermined percentage of the length of a neutral face plate line usedby the manufacturer in forming the prosthetic component can be 100% orless, 90%-99%, or 80%-99%. The predetermined percentage can be greaterthan, equal to, or less than 100%, and can take into account a range ofdata values observed when analyzing a number of images for themeasurement of interest. For example, the predetermined percentage canbe selected to include any number of standard deviations above a mean ofthe collected measurement data. The joint can be arthritic. In one form,at least a section of the base surface of the prosthetic component isflat. For example, the base surface of the prosthetic component can beflat around a central post that extends away from the base surface ofthe prosthetic component. The neutral face plate line can correspond toa width of a flat neutral face plate formed by removing a portion of thebone during arthroplasty. In one version of the method, the bone is thescapula, and the joint is the shoulder. The prosthetic component can bea glenoid component. The image can be a computed tomography scan slice,and the reference angle can be 90 degrees. In one version of the method,the neutral face plate line is a straight line positioned completelywithin a perimeter of the image of the bone from the first border of thebone to the second border of the bone. At least a section of thestraight line is spaced from a portion of the perimeter of the image ofthe bone, and the portion of the perimeter of the image of the bonerepresents a natural articular surface of the bone.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. In the method, the prosthetic component is formed to include anarticular section and a projection extending away from the articularsection wherein a length of the projection is a predetermined percentageof a first reference length. The first reference length used by themanufacturer in forming the prosthetic component has been determined by(i) obtaining an image of the bone of the joint, (ii) orienting on theimage a reference angle from a body of the bone to create a neutral faceplate line that extends from a first border of the bone to an oppositesecond border of the bone, (iii) orienting on the image the firstreference line, the first reference line being perpendicular to theneutral face plate line and extending over the bone in the image, (iv)measuring the first reference length of the first reference line fromthe neutral face plate line perpendicular to a depth of a cavity in thebone. The predetermined percentage of the first reference length can be100% or less, 90%-99%, or 80%-99%. The predetermined percentage can begreater than, equal to, or less than 100%, and can take into account arange of data values observed when analyzing a number of images for themeasurement of interest. For example, the predetermined percentage canbe selected to include any number of standard deviations above a mean ofthe collected measurement data. The projection can be a post. In oneversion of the method, the prosthetic component is formed such that thelength of the projection is a predetermined percentage of a secondreference length. The second reference length used by the manufacturerin forming the prosthetic component has been determined by (i) orientingon the image a second reference line parallel to the first referenceline and extending over the bone in the image, (ii) measuring the secondreference length of the second reference line from the neutral faceplate line to the depth of a cavity in the bone. In one version of themethod, the bone is the scapula, and the joint is an arthritic shoulder,and the prosthetic component is a glenoid component. The image can be acomputed tomography scan slice. In one version of the method, theneutral face plate line is a straight line positioned completely withina perimeter of the image of the bone from the first border of the boneto the second border of the bone. At least a section of the straightline is spaced from a portion of the perimeter of the image of the bone,and the portion of the perimeter of the image of the bone represents anatural articular surface of the bone.

In another aspect, the invention provides a method for manufacturing aglenoid component for replacing a part of a scapula of a shoulder jointin a subject. In the method, the glenoid component is formed to have awidth that is a predetermined percentage of a length of a secondreference line. The length of the second reference line used by themanufacturer in forming the prosthetic component has been determined by(i) obtaining an image of the glenoid of the scapula, (ii) orienting onthe image a first reference line that extends perpendicularly from aninferior border of the glenoid image over the scapula in the image, (ii)orienting on the image the second reference line, the second referenceline perpendicularly intersecting the first reference line and extendingfrom a first border of the scapula to an opposite second border of thescapula, and (iii) measuring the length of the second reference line.The predetermined percentage of the length of the second reference linecan be 100% or less, 90%-99%, or 80%-99%. The predetermined percentagecan be greater than, equal to, or less than 100%, and can take intoaccount a range of data values observed when analyzing a number ofimages for the measurement of interest. For example, the predeterminedpercentage can be selected to include any number of standard deviationsabove a mean of the collected measurement data. The second referenceline intersects the first reference line at about 10 to 18 millimetersabove the inferior border of the glenoid image. The second referenceline preferably intersects the first reference line at about 14millimeters above the inferior border of the glenoid image. The imagecan be a computed tomography scan slice.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. In the method, the prosthetic component is formed to include aprotruding section wherein a first length of the protruding section is apredetermined percentage of a length of the third reference line. Thelength of the third reference line used by the manufacturer in formingthe prosthetic component has been determined by (i) obtaining an imageof the bone of the joint, (ii) orienting on the image a first referenceline that extends from a first border of a head of the bone to anopposite second border of the head of the bone, (iii) orienting on theimage a 90 degree reference angle from an inferior position of the firstreference line to create a second reference line that extends over theimage of the bone, (iv) orienting on the image the third reference line,the third reference line extending over the image of the bone from thesecond reference line to a superior aspect of a tuberosity of the bone,and (v) measuring the length of the third reference line. In one versionof the method, the prosthetic component is formed such that a secondlength of the projection is a predetermined percentage of a fourthreference length wherein the second length of the projection isperpendicular to the first length of the projection. The fourthreference length used by the manufacturer in forming the prostheticcomponent has been determined by (i) orienting on the image a fourthreference line perpendicular to the third reference line and extendingover the bone in the image from the third reference line to a perimeterof the bone in the image, and (ii) measuring the fourth reference lineto determine the fourth reference length. In one version of the method,the bone is the humerus, the joint is the shoulder, the length of thethird reference line is a superior-inferior length of a greatertuberosity of the humerus, and the fourth reference length is amedial-lateral length of the greater tuberosity of the humerus. In oneversion of the method, the joint has been fractured, and the protrudingsection includes a plurality of fins for immobilizing fracturefragments.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. In the method, the prosthetic component is formed to include ahead and a stem connected to the head. The head has a longitudinal headaxis and the stem has a longitudinal stem axis. The head axis and thestem axis are angled to create an inclination angle between the headaxis and the stem axis. The inclination angle used by the manufacturerin forming the prosthetic component has been determined by (i) obtainingan image of the bone of the joint, (ii) orienting on the image a firstreference line that extends from a first border of a head of the bone toan opposite second border of the head of the bone, (iii) orienting onthe image a 90 degree reference angle from an inferior position of thefirst reference line to create a second reference line that extends overthe image of the bone, (iv) orienting on the image the third referenceline, the third reference line extending over the image of the bone fromthe second reference line to a superior aspect of a tuberosity of thebone, and (v) measuring an angle between the first reference line andthe third reference line, wherein the angle is equal to the inclinationangle. In one version of the method, the bone is the humerus, and thejoint is an arthritic shoulder. The image can be a computed tomographyscan slice.

In another aspect, the invention provides a method for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject. In the method, the prosthetic component is formed to include anarticular head and an opposed base surface. The head has a longitudinalhead axis, and the head axis and the base surface are angled to createan inclination angle between the head axis and the base surface. Theinclination angle used by the manufacturer in forming the prostheticcomponent has been determined by (i) obtaining an image of the bone ofthe joint, (ii) orienting on the image a first reference line thatextends from a first border of a head of the bone to an opposite secondborder of the head of the bone, (iii) orienting on the image a 90 degreereference angle from an inferior position of the first reference line tocreate a second reference line that extends over the image of the bone,(iv) orienting on the image the third reference line, the thirdreference line extending over the image of the bone from the secondreference line to a superior aspect of a tuberosity of the bone, and (v)measuring an angle between the first reference line and the thirdreference line, the angle being equal to the inclination angle. In oneversion of the method, the bone is the humerus, and the joint is anarthritic shoulder. The image can be a computed tomography scan slice.

These and other features, aspects, and advantages of the presentinvention will become better understood upon consideration of thefollowing detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a shoulderprosthesis suitable for use in the invention.

FIG. 2 shows a tracing of a computed tomography (CT) axialtwo-dimensional (2D) CT slice of the scapula and humerus withmeasurement lines according to the invention shown in broken lines.

FIG. 3 shows a tracing of a 2D CT sagittal slice of the scapula withmeasurement lines according to the invention shown in broken lines.

FIG. 4 shows a tracing of a CT 2D coronal slice of the scapula andhumerus with measurement lines according to the invention shown inbroken lines.

Like reference numerals will be used to refer to like parts from Figureto Figure in the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Looking first at FIG. 1, there is shown one example embodiment of ashoulder prosthesis 10 suitable for use in the invention. The upperportion of the humerus 12 is replaced by a humeral component 14including a stem 16 that extends into a bore formed within the humerus12. Typically, the stem 16 is fixed within the bore formed within thehumerus 12. The stem 16 has a longitudinal stem axis S. A generallyhemispherical head 18 is connected to the stem 16. The stem 16 can bemonolithic with the head 18, or the stem 16 and the head 18 can formedas separate parts. The hemispherical head 18 has a base surface 19 and alongitudinal head axis H. The hemispherical head 18 of the humeralcomponent 14 articulates with a complementary concave section 22 of aglenoid component 24 that is fixed within the glenoid cavity of thescapula 26 (shown cutaway) using cemented or uncemented posts 28. Theglenoid component 24 includes a base surface 27 opposite the concavesection 22 that serves as an articular surface of the glenoid component24.

Proper design and selection of the hemispherical head 18 and the glenoidcomponent 24 can be achieved using the method of the invention. In onenon-limiting example method of the invention, eleven measurements areobtained using CT slices. The eleven measurements are as follows: (1)glenoid version; (2) anterior-posterior (AP) diameter at the articularsurface; (3) anterior-posterior width at a neutral face plate; (4) depthof the glenoid vault from a neutral face plate; (5) depth of the glenoidvault from a neutral face plate with a diameter of the center post (anexample center post diameter being five millimeters); (6)superior-inferior glenoid height; (7) determination of theanterior-posterior width fourteen millimeters from the inferior borderof the glenoid; (8) humeral head diameter; (9) humeral head thickness;(10) greater tuberosity length of the humerus; (11) greater tuberositywidth of the humerus; and (12) humeral inclination.

Various combinations of these measurements are used for manufacturing aprosthetic component for replacing a part of a bone of a joint in asubject (e.g., mammal). The prosthetic component may be formed from, forexample: (i) a metal or metal alloy such as a titanium alloy (e.g.,titanium-6-aluminum-4-vanadium), a cobalt alloy, a stainless steelalloy, or tantalum; (ii) a nonresorbable ceramic such as aluminum oxideor zirconia; (iii) a nonresorbable polymeric material such aspolyethylene; or (iv) a nonresorbable composite material such as acarbon fiber-reinforced polymers (e.g., polysulfone). The prostheticcomponent can be manufactured by machining an article formed from thesematerials, or by molding these materials in a suitable mold.

Examples

The following Examples have been presented in order to furtherillustrate the invention and are not intended to limit the invention inany way.

1. Glenoid Version

Using an axial 2D CT scan of a human shoulder, the mid point of theglenoid was determined. A first line was then drawn through the midpointand parallel to the scapular body. The first line intersects a secondline drawn parallel to the joint surface. The glenoid version was theangle between the first line and the second line, and was recorded indegrees.

2. Anterior-Posterior (AP) Width at the Articular Surface

Using an axial 2D CT scan of a human shoulder, the diameter (AP width)was measured at the mid-point of the glenoid in millimeters.

3. Anterior-Posterior (AP) Width at a Neutral Face Plate

Looking at FIG. 2, an axial 2D CT scan of a human shoulder was obtainedand a 90 degree angle A (shown in broken lines) was oriented from thescapular body 26 and then placed on the glenoid 30 to create a neutralface plate 32 (shown in broken lines) that runs from one side border 34to the other side border 36 of the glenoid 30. This width was thenmeasured in millimeters. This measurement is important to determine thetrue AP width of the glenoid after creating a flat neutral face plate byremoving bone during arthroplasty. This is what occurs at surgeryaccording to the method of the invention, yet this measurement has neverbeen previously described. Prior measurements have been made of thearticular surface only of the glenoid. This explains why many glenoidcomponent sizes are too large. The measurement at a neutral faceplate isusually several millimeters less than the measurement at the articularsurface due to reaming or removing glenoid bone to make the surface flatto place the glenoid component 24.

When manufacturing a glenoid component, a manufacturer can be suppliedwith the length of the neutral face plate 32 which provides a true APwidth of the glenoid after creating a flat neutral face plate byremoving bone during arthroplasty. A predetermined percentage of thelength of the neutral face plate 32 can be used to machine or mold theglenoid component to have a selected width for the base surface 27 (seeFIG. 1).

4. Depth of the Glenoid Vault from a Neutral Face Plate

Still looking at FIG. 2, a line 38 (shown in broken lines) was startedat the neutral face plate 32 and was drawn medially to determine thedepth of the glenoid vault 40. Previous reports have mentioned only thedepth from the articular surface which overstates the depth of theglenoid. This explains why many central posts or peripheral pegs ofglenoid components that are currently in the market are too long andperforate the glenoid. Prior designs have not been designed based onpatients with arthritis and associated bone loss who have undergoneshoulder arthroplasty.

When manufacturing a glenoid component, a manufacturer can be suppliedwith the length of the line 38. A predetermined percentage of the lengthof the line 38 can be used to machine or mold the glenoid component tohave a selected longitudinal length for the post 28 (see FIG. 1).

5. Depth of the Glenoid Vault from a Neutral Face Plate with a Diameterof 5 Millimeters

Still looking at FIG. 2, a five millimeter line 42 (shown in brokenlines) was placed within the vault parallel to the line 38. This willshow one the depth of the glenoid vault that one can drill back to afive millimeter diameter. This allows accurate determination of the safelength for a central post or screw. Other post diameters are allowed inthe design, five millimeters is used only as an example.

When manufacturing a glenoid component, a manufacturer can be suppliedwith the length of the line 42. A predetermined percentage of the lengthof the line 42 can be used to machine or mold the glenoid component tohave a selected length for the post 28 (see FIG. 1).

6. Superior-Inferior Glenoid Length

The height of the glenoid was measured in millimeters.

7. Determination of the AP Width Fourteen Millimeters from the InferiorBorder of the Glenoid

Turning to FIG. 3, a 2D CT scan of a human shoulder was obtained and onthe sagittal cut, an anterior-posterior width on line 46 (shown inbroken lines) was measured. Line 46 was perpendicular to and fourteenmillimeters up line 50 (shown in broken lines) from the inferior border48 of the glenoid 30. This measures the anterior-posterior width of theglenoid fourteen millimeters above the inferior rim of the glenoid. Thisallows determination of the appropriate width of a glenoid base platefor reverse arthroplasty.

When manufacturing a glenoid component, a manufacturer can be suppliedwith the length of the line 46. A predetermined percentage of the lengthof the line 46 can be used to machine or mold the glenoid component tohave a selected width for the base surface 27 (see FIG. 1).

8. Humeral Head Diameter and 9. Humeral Head Thickness

Turning to FIG. 4, a 2D CT scan of a human shoulder was obtained and onthe coronal slice the diameter of the humeral head was measured inmillimeters at line 52 (shown in broken lines). A line 54 (shown inbroken lines) was then drawn perpendicular from line 52 to the surface56 of the humeral head. The length of line 54 (here measured inmillimeters) gives one the thickness of the humeral head.

10. Greater Tuberosity Length and 11. Greater Tuberosity Width

A 90 degree line 58 (shown in broken lines) was taken off the mostinferior aspect of the humeral head cut. A line 62 (shown in brokenlines) was then placed from the superior aspect of the greatertuberosity (intersection with the superior end point of line 52) tointersect this line 58. This line 62 shows the true distance of thegreater tuberosity in length (superior-inferior). Next a line 64 (shownin broken lines) was taken 90 degrees to this line 62 to show themaximum diameter of the greater tuberosity. This line 64 shows the truedistance of the greater tuberosity in width (medial-lateral). Thisfacilitates designing a humeral component that maximizes tuberosityhealing as well as anatomic component shape. This data also facilitatesthe design of different size humeral components specifically forfracture cases to improve tuberosity healing. This would includedifferent size “fins” or other components to accommodate and securefracture fragments based on the size of the patient.

12. Measurement of Humeral Inclination

On FIG. 4, taking the angle B between lines 52 and 62 in degrees andadding 90° defines the inclination angle of the humeral head in degrees(i.e., angle B in degrees+90°=the inclination of the humeral head). Thismeasurement can determine the true range of inclination necessary forhumeral component design.

When manufacturing a humeral component, a manufacturer can be suppliedwith the inclination angle of the humeral head. The inclination angle ofthe humeral head can be used to machine or mold the humeral component tohave a selected angle, or a selected range of angles (for adjustablehumeral inclination) between the longitudinal head axis H (see FIG. 1)and the longitudinal stem axis S (see FIG. 1) or the longitudinal headaxis H and the base surface 19 (see FIG. 1).

Results

Using the measurement technique of Examples 1-12, a review of 800patients who have undergone shoulder arthroplasty (436 total shoulderarthroplasties, 210 reverse shoulder arthroplasties, and 154hemiarthroplasties) was completed and is shown in Table 1 below. Inaddition, statistical analysis revealed that when evaluating forspecific anatomic ratios there were very tight confidence intervals.This can be further used to ensure proper component design as shown inTable 2.

TABLE 1 Anatomic Measurements of 800 Shoulders 10th 90th Variable MeanStd Dev Median Minimum Maximum Pctl Pctl 1. Glenoid version (degrees)10.66 9.68 10.00 −27.00 49.00 0.00 24.00 2. AP width at articularsurface (mm) 28.71 4.32 28.50 12.40 41.20 23.30 34.20 3. AP width at aneutral faceplate (mm) 24.59 3.83 24.70 12.00 36.90 19.80 29.30 4. Vaultdepth from a neutral face plate (mm) 21.79 4.30 22.00 6.10 37.00 16.3027.20 5. Vault depth to a 5 mm diameter (mm) 16.07 4.2 16.30 2.00 27.3010.80 21.50 6. Superior-Inferior: Glenoid Height (mm) 34.61 4.4 34.2024.00 50.10 29.10 40.60 7. AP width 14 mm from inferior glenoid rim (mm)26.78 3.14 26.80 15.00 35.20 22.80 30.80 8. Humeral head diameter (mm)43.47 4.31 43.00 32.80 56.00 38.30 49.60 9. Humeral head thickness (mm)22.11 2.76 22.20 14.20 29.70 18.80 25.60 10. Greater tuberositysuperior-inferior (mm) 33.61 4.54 33.10 21.00 47.00 28.00 40.00 11.Greater tuberosity medial-lateral (mm) 11.29 2.01 11.00 6.30 18.00 8.9014.00 12. Humeral Inclination (degrees) 129.13 5.72 129.00 115.00 145.00121.00 137.00 The 10th and 90th percentile refer to the range of data.

TABLE 2 Overall-95% Overall Confidence Ratio Ratio Intervals Humeralhead diameter/Humeral head 1.98 1.97, 2.00 thickness Greater tuberositymedial-lateral (width)/ 0.337 0.334, 0.341 Greater tuberositysuperior-inferior (height) AP width at a neutral faceplate/ 1.16 1.14,1.18 Vault depth from a neutral faceplate

Thus, the invention provides a method for the optimization of shoulderarthroplasty component design. Use of this method and the data that itprovides gives unique insight into the number, size and shape of glenoidcomponents for total shoulder arthroplasty and reverse arthroplasty aswell as humeral heads for shoulder arthroplasty and resurfacingarthroplasty. This method also provides valuable information for theoptimal design, shape, and size of the proximal humeral body for afracture stem to maximize tuberosity healing and humeral componentdesign for hem iarthroplasty/total shoulder arthroplasty. In the courseof new product development, this method is a valuable resource that canbe used to radiographically evaluate each new component design to ensureoptimal fit prior to component production and product launch. While theinvention is described herein as a method for the optimization ofshoulder arthroplasty component design, it can be used for other joints(e.g., hip, knee, elbow, foot, ankle, etc. . . . ).

Although the present invention has been described in detail withreference to certain embodiments, one skilled in the art will appreciatethat the present invention can be practiced by other than the describedembodiments, which have been presented for purposes of illustration andnot of limitation. Therefore, the scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

What is claimed is:
 1. A method for manufacturing a prosthetic componentfor replacing a part of a bone of a joint in a subject, the methodcomprising: forming the prosthetic component to include a proximalsection and a stem connected to the proximal section, the proximalsection having a longitudinal proximal section axis and the stem havinga longitudinal stem axis, the proximal section axis and the stem axisbeing angled to create an inclination angle between the proximal sectionaxis and the stem axis, the inclination angle having been determined by(a) obtaining a coronal image of the bone of the joint; (b) orienting onthe image a first reference line that extends from a first border of ahead of the bone to an opposite second border of the head of the bone;(c) orienting on the image a 90 degree reference angle from an inferiorposition of the first reference line to create a second reference linethat extends over the image of the bone; (d) orienting on the image athird reference line, the third reference line extending over the imageof the bone from the second reference line to a superior aspect of atuberosity of the bone; (e) measuring a reference angle between thefirst reference line and the third reference line; and (f) determiningthe inclination angle from the reference angle.
 2. The method of claim 1wherein the proximal section comprises an articular surface.
 3. Themethod of claim 2 wherein the articular surface is convex.
 4. The methodof claim 2 wherein the articular surface is concave.
 5. The method ofclaim 1 wherein the bone is a humerus, and the joint is a shoulder. 6.The method of claim 1 wherein the image is a computed tomography scanslice.